The present invention relates to a method for shaping a rectangular carton blank for the purpose of forming straight edges and flat side walls. The invention additionally relates to an apparatus for practicing the above method.
In the packaging art wherein cut tubular carton blanks are shaped into rectangular cartons, particularly light-weight cartons often exhibit the effect that the side walls are uneven and are easily deformed by pourable contents. From the point of view of a representative display of the goods to be sold, this is unfavorable and it is difficult to pack a plurality of such deformed cartons in cases.
According to British Patent Application No. 2,004,832, published Apr. 11, 1979, it is known to erect a flat folded tubular carton blank by pulling one of the walls of the carton blank, by means of suction cups, between spaced holders so as to partially open the blank. In an erecting station, one wall is pulled against a breaker rod and the conveyor belt presses together the leading and trailing edges of the wall resting on the conveyor belt so that the upper carton wall is bent outwardly. In this state, the carton blank is transferred to opener elements and introduced into a further processing station.
In this way, a carton blank can be opened from its folded state with the walls contacting one another. But the edges are produced only to the extent permitted by the impressed fold lines between the flat juxtaposed walls and the walls are not smoothed by the above-described process.